The present invention is directed toward a disposable device suitable for use in an automated solid-phase immunoassay. The device is designed to have two wells, one in which a sample material can be treated with reagents to perform a solid-phase assay and another in which the results of that assay can be read. The sample mixture is transferred from the reaction well to the read well by a non-contact means using jets of fluid to move the reactants between the two wells.
Techniques for performing an immunoassay are generally well known in the art. For example, conventional enzyme immunoassay procedures involve a series of steps wherein an analyte in a sample material is initially bound to a corresponding antigen or antibody reagent. A second antigen or antibody is then introduced into the sample which has been labeled or conjugated with an enzyme or other substance capable of detection when treated with an additional suitable indicator reagent such as a chromogen or dye to produce a signal which is then read to indicate the absence or presence of the antigen or antibody in the sample.
Solid-phase immunoassay procedures are preferred over other diagnostic methods because of their safety, ease of use, specificity and sensitivity. Moreover, when employing a solid-phase immunoassay procedure, the result is easily observed by instruments which increases the accuracy of the procedure.
One form of a conventional solid-phase immunoassay is a "sandwich assay" which involves contacting a test sample suspected of containing an antibody or antigen with a substantially solid inert plastic or glass bead or other support material which can be coated with a protein or another substance capable of binding the antigen or antibody to the surface of the support. After the antibody or antigen is bound to the support material it is treated with a second antigen or antibody, which is conjugated with an enzyme, a fluorophore or a chemiluminescent label. The second antigen or antibody then becomes bound to the corresponding antibody or antigen on the support. Following one or more washing steps to remove any unbound material in an enzyme immunoassay, an indicator substance, for example, a chromogenic substrate, is added which reacts with the enzyme to produce a color change. The color change can be observed visually or more preferably by an instrument to indicate the presence or absence of an antibody or antigen in the sample. For solid phase fluorescence or chemiluminescence immunoassays, fluorescent labeled moeities can be monitored using excitation at an appropriate wavelength, while chemiluminescent labeled antigens or antibodies can be followed after reaction by chemically activating the chemiluminescent labels to generate light which can be detected by photometric means.
Many procedures and apparatus have been designed to perform solid-phase immunoassays. U.S. Pat. No. 4,632,901 discloses an apparatus having a porous filter containing a bound receptor for complexing an analyte. In this apparatus an absorbent material is positioned below the porous filter to assist the fluid sample in flowing through the filter. A labeled antibody is then added to the porous filter to detect the presence or absence of the analyte.
In another approach, European Patent Application No. 0131934 discloses an assay device having a plurality of aligned adjacent reaction wells located on its top surface which empty through a filter membrane located above a waste reservoir. A solid-phase fluorescent immunoassay reaction mixture is placed in the well and drawn through the membrane by applying reduced pressure to the waste reservoir to separate a solid-phase reaction product from a liquid-phase reaction product so that the solid-phase reaction product can be observed. This approach, however, has a serious limitation. Sample and microparticle incubation takes place in the same reaction well which can lead to non-specific binding of conjugates to the membrane filter contributing to the background of the assay and limits its sensitivity.
Other methods for performing a solid phase enzyme immunoassay are disclosed in U.S. Pat. Nos. 4,587,102, and 4,552,839, and European Patent Application 0200381. These references generally disclose procedures for employing particles having a receptor to bind an analyte which is subsequently labeled and deposited on a matrix or other support system. The particle complex is treated with an indicator substance to indicate the presence or absence of an analyte.
While many immunoassay procedures and devices have proved useful, better procedures and devices are continually being sought to improve reliability, efficiency and sensitivity. The present invention provides all these improvements.